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.\" RCSid "$Id$" |
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.TH RPIECE 1 5/25/05 RADIANCE |
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.TH RTCONTRIB 1 5/25/05 RADIANCE |
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.SH NAME |
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rtcontrib - compute contributions in a RADIANCE scene |
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rtcontrib - compute contribution coefficients in a RADIANCE scene |
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.SH SYNOPSIS |
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.B rtcontrib |
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[ |
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.B "\-n nprocs" |
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][ |
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.B \-V |
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][ |
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.B \-c |
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][ |
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.B \-fo |
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| |
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.B \-r |
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][ |
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.B "\-e expr" |
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][ |
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.B "\-f source" |
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][ |
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.B "\-o fspec" |
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.B "\-o ospec" |
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][ |
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.B "\-b binv" |
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][ |
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.B "\-bn nbins" |
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] |
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.B "\-m mod .." |
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{ |
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.B "\-m mod | \-M file" |
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} |
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.. |
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[ |
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.B $EVAR |
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] |
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rtrace options |
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] |
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.B octree |
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.br |
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.B "rtcontrib [ options ] \-defaults" |
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.SH DESCRIPTION |
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.I Rtcontrib |
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computes ray contributions (i.e., color coefficients) |
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computes ray coefficients |
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for objects whose modifiers are named in one or more |
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.I \-m |
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settings. |
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These modifiers are usually materials associated with |
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light sources or sky domes, and must directly modify some geometric |
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primitives to be considered in the output. |
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The computed contributions can then be used in linear combination to |
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A modifier list may also be read from a file using the |
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.I \-M |
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option. |
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The RAYPATH environment variable determines directories to search for |
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this file. |
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(No search takes place if a file name begins with a '.', '/' or '~' |
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character.)\0 |
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.PP |
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By setting the boolean |
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.I \-V |
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option, you may instruct |
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.I rtcontrib |
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to report the contribution from each material rather than the ray |
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coefficient. |
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This is particularly useful for light sources with directional output |
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distributions, whose value would otherwise be lost in the shuffle. |
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With the default |
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.I -V- |
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setting, the output of rtcontrib is a coefficient that must be multiplied |
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by the radiance of each material to arrive at a final contribution. |
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This is more convenient for computing daylight coefficeints, or cases |
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where the actual radiance is not desired. |
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Use the |
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.I -V+ |
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setting when you wish to simply sum together contributions |
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(with possible adjustment factors) to obtain a final radiance value. |
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Combined with the |
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.I \-i |
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or |
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.I \-I |
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option, irradiance contributions are reported by |
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.I \-V+ |
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rather than radiance, and |
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.I \-V- |
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coefficients contain an additonal factor of PI. |
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.PP |
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The output of |
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.I rtcontrib |
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has many potential uses. |
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Source contributions can be used as components in linear combination to |
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reproduce any desired variation, e.g., simulating lighting controls or |
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changing sky conditions via daylight coefficients. |
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More generally, |
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.I rtcontrib |
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may be used to compute input-output relationships in optical |
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systems, such as light pipes and shading devices. |
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can be used to compute arbitrary input-output relationships in optical |
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systems, such as luminaires, light pipes, and shading devices. |
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.PP |
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Setting the |
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.I \-c |
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option instructs |
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.I rtcontrib |
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to accumulate values rather than reporting one record per ray. |
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With this option, only a single record will be produced at the very |
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end, corresponding to the sum of all rays given on the input. |
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This is equivalent to passing all the output records through a program like |
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.I total(1) |
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to sum RGB values together, but is much more efficient. |
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Using this option, it is possible to reverse sampling, sending rays from |
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a parallel source such as the sun to a diffuse surface, for example. |
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Care must be taken to perform normalization based on the |
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radiation density and the number of rays sampled. |
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.PP |
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.I Rtcontrib |
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calls |
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.I rtrace(1) |
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to calculate the contributions for each input ray, |
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and the output tallies are sent to one or more files according to the |
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with the \-oTW (or \-oTV) option to calculate the daughter ray |
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contributions for each input ray, and the output tallies |
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are sent to one or more destinations according to the given |
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.I \-o |
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specification. |
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If a destination begins with an exclamation mark ('!'), then |
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a pipe is opened to a command and data is sent to its standard input. |
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Otherwise, the destination is treated as a file. |
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An existing file of the same name will not be clobbered, unless the |
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.I \-fo |
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option is given. |
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If instead the |
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.I \-r |
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option is specified, data recovery is attempted on existing files. |
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(If |
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.I \-c |
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is used together with the |
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.I \-r |
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option, existing files are read in and new ray evaluations are added |
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to the previous results, providing a convenient means for |
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progressive simulation.)\0 |
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If an output specification contains a "%s" format, this will be |
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replaced by the modifier name. |
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The |
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a "bin number" within each object if finer resolution is needed, and |
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this will be applied to a "%d" format in the output file |
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specification if present. |
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(The actual bin number is computed at run time based on ray direction |
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and surface intersection, as described below.)\0 |
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The actual bin number is computed at run time based on ray direction |
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and surface intersection, as described below. |
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If the number of bins is known in advance, it should be specified with the |
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.I \-bn |
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option, and this is critical for output files containing multiple values |
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per record. |
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Since bin numbers start from 0, the bin count is always equal to |
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the last bin plus 1. |
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Set the this value to 0 if the bin count is unknown (the default). |
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The most recent |
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.I \-b |
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.I \-b, |
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.I \-bn |
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and |
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.I \-o |
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options to the left of each |
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.I \-m |
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setting affect only that modifier. |
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(The ordering of other options is unimportant.)\0 |
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The ordering of other options is unimportant, except for |
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.I \-x |
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and |
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.I \-y |
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if the |
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.I \-c |
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is present, when they control the resolution string |
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produced in the corresponding output. |
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.PP |
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If a |
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.I \-b |
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will be assigned to Dx, Dy, and Dz. |
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These parameters may be combined with definitions given in |
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.I \-e |
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options and files read in |
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arguments and files read using the |
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.I \-f |
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options, to compute the bin, which will be |
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option. |
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The computed bin value will be |
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rounded to the nearest whole number. |
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This mechanism allows the user to define precise regions or directions |
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they wish to accumulate, such as the Tregenza sky discretization, |
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which would be otherwise impossible to specify |
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as a set of RADIANCE primitives. |
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The rules and predefined functions available for these expressions are |
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described in the |
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.I rcalc(1) |
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man page. |
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Unlike |
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.I rcalc, |
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.I rtcontrib |
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will search the RADIANCE library directories for each file given in a |
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.I \-f |
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option. |
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.PP |
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If no |
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.I \-o |
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specification is given, results are written on the standard output in order |
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of modifier (as given on the command line) then bin number. |
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Concatenated data is also sent to a lone output file (i.e., an initial |
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Concatenated data is also sent to a single destination (i.e., an initial |
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.I \-o |
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specification without formatting strings). |
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If a "%s" format appears but no "%d" in the |
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To compute the proportional contributions from sources modified |
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by "light1" vs. "light2" on a set of illuminance values: |
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.IP "" .2i |
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rtcontrib -I+ @render.opt -o c_%s.dat -m light1 -m light2 scene.oct < test.dat |
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rtcontrib \-I+ @render.opt \-o c_%s.dat \-m light1 \-m light2 scene.oct < test.dat |
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.PP |
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To generate a pair of images corresponding to these two lights' |
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contributions: |
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.IP "" .2i |
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vwrays -ff -x 1024 -y 1024 -vf best.vf | |
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rtcontrib -ffc `vwrays -d -x 1024 -y 1024 -vf best.vf` |
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@render.opt -o c_%s.pic -m light1 -m light2 scene.oct |
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vwrays \-ff \-x 1024 \-y 1024 \-vf best.vf | |
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rtcontrib \-ffc `vwrays \-d \-x 1024 \-y 1024 \-vf best.vf` |
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@render.opt \-o c_%s.pic \-m light1 \-m light2 scene.oct |
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.PP |
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These images may then be recombined using the desired outputs |
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of light1 and light2: |
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.IP "" .2i |
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pcomb -c 100 90 75 c_light1.pic -c 50 55 57 c_light2.pic > combined.pic |
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pcomb \-c 100 90 75 c_light1.pic \-c 50 55 57 c_light2.pic > combined.pic |
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.PP |
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To compute an array of illuminance contributions according to a Tregenza sky: |
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.IP "" .2i |
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rtcontrib -b tbin -o sky.dat -m skyglow -b 0 -o ground.dat -m groundglow |
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@render.opt -f tregenza.cal scene.oct < test.dat |
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rtcontrib \-I+ \-b tbin \-o sky.dat \-m skyglow \-b 0 \-o ground.dat \-m groundglow |
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@render.opt \-f tregenza.cal scene.oct < test.dat |
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.SH ENVIRONMENT |
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RAYPATH path to search for \-f and \-M files |
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.SH AUTHOR |
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Greg Ward |
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.SH "SEE ALSO" |
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cnt(1), getinfo(1), pcomb(1), pfilt(1), ra_rgbe(1), |
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rcalc(1), rpict(1), rtrace(1), vwrays(1), ximage(1) |
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rcalc(1), rpict(1), rtrace(1), total(1), vwrays(1), ximage(1) |
